What is Best Evening Primrose Oil in UK? The oil that is pressed from the seeds of the Evening Primrose plant has long been used to promote good health. Best evening primrose oil UK manufactured is a rich source of Gamma Linolenic Acid (GLA), an essential omega 6 fatty acid that is believed to support the heart, hormonal balance, and the appearance of skin. The body does not produce GLA so sufficient levels need to be consumed through the diet or supplements. The Health Benefits Of Evening Primrose Oil GLA regulates the body’s production of prostaglandins, which are hormone-like substances that act as chemical messengers between cells. Experts believe that these prostaglandins help to maintain hormonal balance throughout the month and, for this reason, many female customers choose to take these capsules to counter the effects of premenstrual syndrome (PMS).